// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_SPDY_HPACK_HPACK_DECODER_INTERFACE_H_
#define NET_SPDY_HPACK_HPACK_DECODER_INTERFACE_H_

// HpackDecoderInterface is the base class for HPACK block decoders.
// HPACK is defined in http://tools.ietf.org/html/rfc7541

#include <stddef.h>

#include <memory>

#include "net/base/net_export.h"
#include "net/spdy/hpack/hpack_header_table.h"
#include "net/spdy/spdy_header_block.h"
#include "net/spdy/spdy_headers_handler_interface.h"

namespace net {

class NET_EXPORT_PRIVATE HpackDecoderInterface {
public:
    virtual ~HpackDecoderInterface() { }

    // Called upon acknowledgement of SETTINGS_HEADER_TABLE_SIZE.
    virtual void ApplyHeaderTableSizeSetting(size_t size_setting) = 0;

    // If a SpdyHeadersHandlerInterface is provided, the decoder will emit
    // headers to it rather than accumulating them in a SpdyHeaderBlock.
    virtual void HandleControlFrameHeadersStart(
        SpdyHeadersHandlerInterface* handler)
        = 0;

    // Called as HPACK block fragments arrive. Returns false if an error occurred
    // while decoding the block.
    virtual bool HandleControlFrameHeadersData(const char* headers_data,
        size_t headers_data_length)
        = 0;

    // Called after a HPACK block has been completely delivered via
    // HandleControlFrameHeadersData(). Returns false if an error occurred.
    // |compressed_len| if non-null will be set to the size of the encoded
    // buffered block that was accumulated in HandleControlFrameHeadersData(),
    // to support subsequent calculation of compression percentage.
    // Discards the handler supplied at the start of decoding the block.
    // TODO(jamessynge): Determine if compressed_len is needed; it is used to
    // produce UUMA stat Net.SpdyHpackDecompressionPercentage, but only for
    // SPDY3, not HTTP2.
    virtual bool HandleControlFrameHeadersComplete(size_t* compressed_len) = 0;

    // Accessor for the most recently decoded headers block. Valid until the next
    // call to HandleControlFrameHeadersData().
    // TODO(birenroy): Remove this method when all users of HpackDecoder specify
    // a SpdyHeadersHandlerInterface.
    virtual const SpdyHeaderBlock& decoded_block() = 0;

    virtual void SetHeaderTableDebugVisitor(
        std::unique_ptr<HpackHeaderTable::DebugVisitorInterface> visitor)
        = 0;

    // How much encoded data this decoder is willing to buffer. Defaults to 32 KB.
    // See FLAGS_gfe2_reloadable_flag_remove_hpack_decode_buffer_size_limit, which
    // is increasing this to twice the decoded limit.
    virtual void set_max_decode_buffer_size_bytes(
        size_t max_decode_buffer_size_bytes)
        = 0;
};

} // namespace net

#endif // NET_SPDY_HPACK_HPACK_DECODER_INTERFACE_H_
